Biometrics authentication is a method for identifying a person by using an identification target of the living body of the person. Blood vessels of a finger are one identification target of a living body.
For example, an authentication apparatus that generates a three-dimensional image by combining images of different sides of a fingertip and uses the three-dimensional image as an identification target has been suggested (for example, see Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-175529.
Incidentally, an object-shape generation method called a view-volume intersection method (Shape From Silhouette method) exists. The view-volume intersection method is a method for generating, in accordance with images of an object from a plurality of viewpoints, positional information of a camera, and the like, the shape of the target object by causing a region in which all the silhouettes in the individual images intersect with each other within a target space to remain as an object region.
When a three-dimensional blood vessel image is generated using the view-volume intersection method, compared with a two-dimensional blood vessel image (entire-circumference development image), the number of parameters serving as identification targets increases. Hence, it is considered that the authentication accuracy improves.
However, portions of a living body other than blood vessels are not hollow and are occupied by individual tissues such as fat. Therefore, for example, as shown in FIG. 1, an optical image pickup camera might not be able to project a blood vessel portion existing on the back side of an image pickup surface.
In this case, with the view-volume intersection method, a blood vessel portion on the back side of the image pickup surface that is not projected to the image pickup surface is not a region in which all the silhouettes in individual images intersect with each other within a target space. Thus, the region does not remain as an object region. As a result, there is a problem in that a shape different from that of the actual blood vessel may be generated.